There are known various types of filters for use in agricultural, domestic and industrial applications. One particularly successful type of filter is the disc filter, which is exemplified in some of the following U.S. patents of the present applicant: U.S. Pat. Nos. 4,005,884; 4,012,176; 4,026,806; 4,042,504; 4,045,345; 4,067,812; 4,077,371; 4,207,181; 4,271,018; 4,295,963; 4,312,374.